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Layer-structured 3D Nanohybrid MoS2@rGO on Nickel Foam for High Performance Energy Storage Applications

Ravindra N. Bulakhea, Van Hoa Nguyenb and Jae-Jin Shima*

aSchool of Chemical Engineering, Yeungnam University, Gyeongsan, Gyeongbuk 38541, Republic of Korea

bDepartment of Chemistry, Nha Trang University, 2 Nguyen Dinh Chieu, Nha Trang, Vietnam

Supplementary information

1) LBL method

A layer by layer (LBL) technique was employed to coat the electrode electrostatically

with GO (Fig. S1). The GO dispersion was prepared by adding 100 mg in 20 ml deionized

water. The GO solution was stirred at 700 rpm for one hour until it become a colloidal

suspension. Briefly, the cleaned nickel foam (NF) was dipped in a colloidal GO

suspension for 10 min, washed with D.I. water, and dried in an oven. One cycle of this

procedure gave a film composed of a monolayer graphene oxide, and repetitive (5–10)

cycles, a multilayer GO film. The deposited films were reduced using a reducing agent.

Chemical reduction was conducted by dipping multi-layered GO films in an aqueous

solution of 0.1 M N2H4 (hydrazine) for 24 h at 70° C, followed by washing with D.I.

water.

Electronic Supplementary Material (ESI) for New Journal of Chemistry.This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2016

ARTICLE Journal Name

2 | J. Name., 2012, 00, 1-3 This journal is © The Royal Society of Chemistry 20xx



Fig. S1: Schematic of the coating process of GO by LBL method.

2) SILAR method

In 1985, Nicolau introduced the SILAR method (Fig. S2) to grow polycrystalline or epitaxial thin films of water-insoluble ionic or covalent compounds of the CmAn type by heterogeneous chemical reactions at the solid-solution interface between the adsorbed cations (CLp)n+ and anions (AL’q)m̶ according to eq. 1.1

m(CLp)n+ + n(AL’q) m-→ CmAn↓ + mpL + nqL’ ..................(1)

where Lp and L’q are ligands. This method involves the alternative immersion of the current collector in a solution containing a soluble salt of the cation and anion of the compounds to be grown. This aqueous solution phase has been reported for the deposition of MoS2 on stainless steel substrates to produce large volumes of monolayers and a few layers that can be deposited onto a substrate to form films.

Journal Name ARTICLE




Fig.S2: Schematic diagram of the coating process of MoS2@rGO by SILAR method [2].

Analytical reagent ammonium molybdate [(NH4)6Mo7O24·4H2O] and sodium sulfide [Na2S·H2O] were used in the deposition of the MoS2 3D electrode. The cation precursor was 0.01 M ammonium molybdate solution. The pH was adjusted to 3 by adding dilute

sulfuric acid. The source of sulfur ions was 1 M sodium sulfide (pH ∼ 13.5). Prepared

solutions were taken into beakers and D.I. water was used for rinsing. After every ten deposition cycles, the D.I. water for rinsing was replaced. Deposition was carried out at room temperature (27◦ C) using unstirred reaction solutions. By making several trials of the time durations for adsorption, reaction and rinsing were optimized. The chemically reduced rGO-decorated 3D porous nickel foam (rGO@NF) was immersed in 0.01 M ammonium molybdate for 25 s, and adsorbed ammonium molybdate (molybdenum complex).

The rGO@NF substrate was rinsed with D.I. water for 30 s to remove the desorbed ions. The substrates were immersed in a 0.1 M sodium sulfide solution for 25 s, where the S2− ions were adsorbed and reacted with Mo4+ ions on the rGO@NF substrate to decorate with MoS2 on 3D porous rGO@NF. The unreacted S2− ions were removed by rinsing the substrates in D.I. water for 30 s. By repeating the SILAR deposition cycles 30-50 times, homogeneous, strongly adherent, and compactly stacked MoS2 layers on NF were obtained.





3) SAED pattern

Fig. S3 shows the selected area energy dispersion (SAED) pattern of MoS2@rGO electrode, it confirms the polycrystalline nature of the MoS2@rGO materials.

Fig. S3: Selected area energy dispersion (SAED) pattern of MoS2@rGO electrode.

4) Elemental mapping

In Figs. S4 (a-d), C, Mo, and S were distributed over the same area, verifying the

formation of MoS2 on the rGO surface. The peaks for C, Mo, and S in Fig. S4 (e) also

confirm the formation of the composite. The peaks around 8 and 9 were formed due

to the copper grid that held the sample.





Fig.S4 TEM image of MoS2@rGO (individual rGO sheet decorated by MoS2) (a); EDS of C (b), Mo (c), S (d) elemental maps and EDS spectra (e) taken from the same area.

5) Equations for supercapacitor calculations

The specific capacitance Csp was calculated by eq. S1:

(S1) 𝐶𝑠𝑝 =

𝑉2

∫𝑉1

𝑖 𝑑𝑉

(𝑉2 ‒ 𝑉1)𝑣𝑚

where i represents current response to the given voltage (V), V1 and V2 are the lower and upper potential limits, respectively, is the scan rate, and m is the mass of the electrode.

Specific capacitance from the charge-discharge plot was calculated by eq. S2:

(S2) 𝐶𝑠𝑝 =

𝑖𝑡𝑚∆𝑣

where t is the discharge time and is the potential window. Here, i/m can be ∆𝑣replaced by the current density. The energy density (E) and power density (P) were calculated using eqs. S3 and S4:





(S3)𝐸 =

12

𝐶𝑠𝑝(∆𝑣)2

(S4)𝑃 =

𝐸𝑡

6) EIS study for electrodes after cyclic stability tests

Fig. S5: Nyquist plots of (a) MoS2 and (b) MoS2@rGO electrodes after 2000 cycles within the frequency range, 40 kHz to 0.1 Hz.

7) SEM images after cycling





Fig. S6: SEM images of (a) MoS2 and (b) MoS2@rGO electrodes after 2000 cycles.

8) Comparison of the reported supercapacitors

Table S1: Supercapacitor properties of the materials reported in the literature and

obtained from this study

MaterialSpecific

capacitance,[F g-1]

Energy density

[Wh kg-1]

Power density

[kW kg-1]

Stability[%]

(Cycles)Ref.

MoS2 composite with graphene or modified graphene

2D MoS2@rGO 265 63 92(1000)

[3]

MoS2@chemically modified graphene

257 - - 93 (1000)

[4]

MoS2@GNS 282 - - 93(1000)

[5]

MoS2@G 270 12.5 2.5 89.6 (1000)

[6]

MoS2@N-G 245 - - 91.3(1000)

[7]

MoS2@G* 46*(50a)

7*c 3.5*e 240* (3500)

[8]

MoS2@S-rGO* 6.56*a 0.58*d 13.4*f 91*(1000)

[9]

MoS2@rGO* 30*b - - - [10]

MoS2@rGO 1064 (4,700a)

47.6(66.8c)

7.63(3.7d)

95(2000)

This work





MoS2 composite with carbon

MoS2@C 210 - - 105(1000)

[11]

MoS2@C 589 72.7 12 104(2000)

[12]

MoS2@N-C 158 - - 89 (1000)

[13]

MoS2@C 201 - - 94.1(1000)

[14]

MoS2@MPC 189 - - 983000

[15]

MoS2/graphene* membranes

4.29*a - - ∼250* (10 000)

[16]

MoS2 composite with polymer

PPY@MoS2 554 49.2 5.8 90(500) [17]

PANI@ MoS2 552 - - 79(6000) [18]

PANI@ MoS2 853 - - 91 (4000) [19]

PANI@ MoS2 567 - - 92(500) [20]

PPy@ MoS2 700 83.3 3.33 854000 [21]

MoS2@PANI 390 - - 86 (1000) [22]

PANI@MoS2@C 678 - - 80 (10,000) [23]

MoS2 composite with metal oxide/sulfide

CeO2@MoS2 102a 84b 3.5e

94

(2000)[24]

Ni3S4@MoS2 1441 - - 90.7 (3000)

[25]

Ni3S2@MoS2 1165 - - 91 (2000)

[26]

MoS2@Ni(OH)2* 516* 5.2*c 11*f 94.2(9000)

[27]

* Values from supercapacitor device,

a: [mF cm-2], b: [F/cm3]; c: [µWh cm-2], d: [mWh cm-3], e: [mW cm-2], and f: [W cm-3]

9) Supercapacitive properties of asymmetric supercapacitors (ASCs) MoS2// rGO:

Electrochemical studies of the MoS2//rGO ASC device: cyclic voltammograms at various potential ranges from 0.8 to 1.8 V in PVA-KOH gel electrolyte at a scan rate of 100 mV s−1, voltammetric response of MoS2//rGO ASC device at different scan rates, galvanostatic charge-discharge curves of





MoS2//rGO within the potential range 1.6 V at different current densities, and Ragone plot for MoS2//rGO ASC device at different current densities. Inset fig d shows capacitance retention of ASC.

Fig. S7: Electrochemical studies of the MoS2//rGO ASC device: (a) cyclic voltammograms within the various potential ranges from 0.8 to 1.8 V in PVA-KOH gel electrolyte at a scan rate of 100 mV s−1, (b) voltammetric response of MoS2//rGO ASC device at different scan rates, (c) galvanostatic charge-discharge curves of MoS2//rGO within the potential range 1.6 V at different current densities, and (d) Ragone plot for MoS2//rGO ASC device at different current densities. The inset of (d) shows the variation of the specific capacitance with different current densities.





10) EIS and Stability studies of MoS2// rGO:The Nyquist plot of MoS2//rGO ASC device and stability studies for 2000 cycles at the current

density 4.5 A g-1.

Fig. S8: Nyquist plot of MoS2//rGO ASC device over the frequency range, 10 MHz to 0.01 Hz (a) and cyclic stability of MoS2//rGO ASC device for 4000th cycles (b).

Notes and References:

1 Y.F. Nicolau, Applications of Surface Science, 1985, 22/23, 1061-1074.2 R. N. Bulakhe, S. Sahoo, T. T. Nguyen, C. D. Lokhande, C. H. Roh, Y. R. Lee and J.-J.

Shim, RSC Adv., 2016, 6, 14844-14851. 3 E. G. Silveira Firmiano da, A. C. Rabelo, C. J. Dalmaschio, A. N. Pinheiro, E. C. Pereira,

W. H. Schreiner and E. R. Leite, Adv. Energy Mater., 2013, 4, 1301380.4 M. H. Yang, J. M. Jeong, Y. S. Huh and B. G. Choi, Compos. Sci. Technol., 2015, 121,

123-128.5 S. Patil, A. Harle, S. Sathaye and K. Patil, Cryst. Eng. Comm., 2014, 16, 10845–10855. 6 R. Thangappan, S. Kalaiselvam, A. Elayaperumal, R. Jayavel, M. Arivanandhan, R.

Karthikeyan and Y. Hayakawa, Dalton Trans., 2016, 45, 2637–2646. 7 B. Xie, Y. Chen, M. Yu, T. Sun, L. Lu, T. Xie, Y. Zhang and Y. Wu, Carbon, 2016, 99, 35-

42. 8 N. Savjani, E. A. Lewis, M. A. Bissett, J. R. Brent, A. W. Dryfe Robert, S. J. Haigh, and P.

O. Brien, Chem. Mater., 2016, 28, 657−664.





9 X. Yuxiu, H. Lei, Z. Qi, X. Shuhua, C. Qi and S. Wangzhou, Appl. Phys. Lett., 2015, 107, 0139061-0139065.

10 S. Gengzhi, L. Juqing, Z. Xiao, W. Xuewan, L. Hai, Y. Yang, H. Wei, Z. Hua and C. Peng, Angew. Chem., 2014, 126, 12784 –12788.

11 B. Hu, X Qin, A. M. Asiri., A. A. Khalid, A. O. Al-Youbib and X. Sun, Electrochim. Acta, 2013, 100, 24– 28.

12 J. Hongmei, C. Liu, T. Wang, J. Chen, M. Zhengning, J. Zhao, W. Hou and G. Yang, Small, 2015, 11(48), 6480–6490.

13 M. H. Yang, S. K. Hwang, J. M. Jeong, Y. S. Huh and B. G. Choi, Synthetic Met., 2015, 209, 528–533.

14 L. Q. Fan, G. J. Liu, C. Y. Zhang, J. H. Wu and Y. L. Wei, Int. J. hydrogen Energ., 2015, 40, 10150 -10157.

15 Q. Weng, X. Wang, X. Wang, C. Zhang, X. Jiang, Y. Bando and D. Golberg, J. Mater. Chem. A, 2015, 3, 3097–3102.

16 M. A. Bissett, I. A. Kinloch and A. W. Dryfe Robert, ACS Appl. Mater. Interfaces, 2015, 7, 17388−17398.

17 S. Faraji and A. F. Nasir, Renew. Sust. Energ. Rev. 2015, 42, 823–834. 18 L. Ren, G. Zhang, Z. Yan, L. Kang, H. Xu, F. Shi, Z. Lei and Z. H. Liu, ACS Appl. Mater.

Interfaces, 2015, 7, 28294−28302. 19 J. Zhu, W. Sun, D. Yang, Y. Zhang, H. H. Hoon, H. Zhang and Q. Yan, Small, 2015,

11(33), 4123–4129. 20 K. Gopalakrishnan, S. Sultan, A. Govindaraj and C.N.R. Rao, Nano Energy, 2015, 12,

52–58. 21 H. Tang, J. Wang, H. Yin, H. Zhao, D. Wang and Z. Tang, Adv. Mater., 2015, 27, 1117–

1123.22 J. Wanga, Z. Wu, K. Hu, X. Chen and H. Yin, J. Alloys Compd., 2015, 619, 38–43.23 C. Yang, Z. Chen, I. Shakir, Y. Xu and H. Lu, Nano Res., 2016, DOI.10-1007/s12274-016-

0983-3.24 N. Li, H. Zhao, Y. Zhang, Z. Liu, X. Gong and Y. Du, Cryst. Eng. Comm., 2016,

10.1039/c5ce02466h.25 Z. Yu, S. Wenping, R. Xianhong, L. Bing, T. T. Hui, G. Guilue, M. Srinivasan, Z. Yun and

Y. Qingyu, Small, 2015, 11(30), 3694–3702.26 J. Wang, D. Chao, J. Liu, L. Lic, L. Lai, J. Lina and Z. Shen, Nano Energy, 2014, 7, 151–160. 27 C. Hao, F. Wen, J. Xiang, L. Wang, H. Hou, Z. Su, W. Hu and Z. Liu, Adv. Funct. Mater., 2014,

24, 6700–6707.

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